Liquid ejecting head, liquid ejecting apparatus and piezoelectric element

ABSTRACT

A piezoelectric element includes a plurality of individual electrodes, a piezoelectric layer formed on each of individual electrodes, and a common electrode which is formed on the piezoelectric layer and is an electrode common to the individual electrodes. Further, a protection film covering a region, which is not covered by the common electrode on the individual electrode, is provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/254,197 filed Sep. 1, 2016, which is a continuation of U.S. patentapplication Ser. No. 14/748,987 filed Jun. 24, 2015, now U.S. Pat. No.9,545,792 issued Jan. 17, 2017, which is a continuation of U.S. patentapplication Ser. No. 14/150,055 filed Jan. 8, 2014, now U.S. Pat. No.9,099,636 issued Aug. 4, 2015, which is a continuation of U.S. patentapplication Ser. No. 13/684,750 filed Nov. 26, 2012, now U.S. Pat. No.8,651,627 issued Feb. 18, 2014, which claims priority to Japanese PatentApplication No. 2011-258608, filed Nov. 28, 2011, all of which arehereby incorporated by reference herein in their entireties.

BACKGROUND 1. Technical Field

The present invention relates to a liquid ejecting head, a liquidejecting apparatus and a piezoelectric element.

2. Related Art

A piezoelectric element, which has the characteristics of being chargedwhen the crystal is distorted and of being distorted when placing in anelectric field, is widely used in liquid ejecting apparatuses such as anink jet printer, an actuator, a sensor or the like.

In addition, the configuration of the piezoelectric element, of which alower electrode is set as an individual electrode for each piezoelectriclayer and an upper electrode is set as a common electrode which iscommon with respect to a plurality of individual electrodes, is known(for example, in JP-A-2010-42683).

In the piezoelectric element having the upper electrode as the commonelectrode, a crack or burnout may occur in a region of the piezoelectriclayer which is not covered with the upper electrode. As a cause thereof,it is thought that the composition of the piezoelectric layer isunstable by chemicals or the like used when patterning of the upperelectrode or wiring.

SUMMARY

An advantage of some aspects of the invention is to improve thestability of at least a piezoelectric element, a liquid ejecting headand a liquid ejecting apparatus.

According to an aspect of the invention, there is provided apiezoelectric element including a plurality of individual electrodes; apiezoelectric layer formed on the individual electrodes; a commonelectrode formed on the piezoelectric layer and is an electrode commonto the individual electrodes; and a protection film covering a region ofthe piezoelectric layer which is not covered by the common electrode onthe individual electrodes.

In the invention having the configuration described above, thepiezoelectric element is configured of the upper electrode as the commonelectrode. In addition, the protection film covers the region of thepiezoelectric layer which is not covered by the common electrode on theindividual electrodes. Thus, cracking or burnout may be decreased at theregion which is not covered by the common electrode on the individualelectrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIGS. 1A and 1B are a partial top view and a vertical cross-sectionalview respectively illustrating a main portion of a piezoelectric elementincluded in a liquid ejecting head according to an embodiment of theinvention.

FIG. 2 is an exploded perspective view illustrating an exploded ink jettype recording head that is an example of the liquid ejecting head.

FIGS. 3A to 3C are cross-sectional views for explaining a manufacturingprocess of the recording head.

FIGS. 4A to 4C are cross-sectional views for explaining a manufacturingprocess of the recording head.

FIG. 5 is an external view of a recording apparatus (a liquid ejectingapparatus) having the recording head described above.

FIGS. 6A to 6C are cross-sectional views for explaining a manufacturingprocess of the recording head.

FIGS. 7A to 7C are cross-sectional views for explaining a manufacturingprocess of the recording head.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, the invention is described in detail based on embodiments.Configurations described in the embodiments are merely examples and theinvention is not limited to the examples.

1. Configuration of Liquid Ejecting Head and Piezoelectric Element

FIGS. 1A and 1B are a partial top view and a vertical cross-sectionalview respectively illustrating a main portion of a piezoelectric element3 included in a liquid ejecting head according to an embodiment of theinvention. In addition, FIG. 2 is an exploded perspective viewillustrating an exploded ink jet type recording head 1 that is anexample of the liquid ejecting head. FIGS. 3A to 3C are cross-sectionalviews for explaining a manufacturing process of the recording head 1.Further, FIGS. 4A to 4C are cross-sectional views for explaining amanufacturing process of the recording head 1.

The recording head (the liquid ejecting head) 1 illustrated in FIG. 2includes a piezoelectric element 3 having a piezoelectric layer 30,electrodes 20 and 40, and a pressure generation chamber 12 whichcommunicates with a nozzle opening 71 and in which pressure change isgenerated by the piezoelectric element 3. More specifically, thepiezoelectric element 3 is configured by laminating a lower electrode20, the piezoelectric layer 30 and an upper electrode 40 in this orderon a vibration plate 16 including an elastic film.

In addition, a flow path formation substrate 10 is fixed in a side wherethe piezoelectric element 3 of the vibration plate 16 is not laminated.A plurality of pressure generation chambers 12 is arranged in parallelin the width direction thereof at the flow path formation substrate 10.In addition, a communication path 13 is formed at a region outside thepressure generation chamber of the flow path formation substrate 10 inthe longitudinal direction. The communication path 13 is communicatedwith the pressure generation chamber 12 via an ink supply path 14provided for each pressure generation chamber 12.

In addition, a nozzle plate 70 is fixed in a side of the flow pathformation substrate 10 where the vibration plate 16 is not fixed. Aplurality of nozzle openings 71, through which ink is discharged andwhich configures a portion of the flow path, is penetrated into thenozzle plate 70. Further, a protection substrate 50, where a compliancesubstrate 60 is fixed, is fixed in a side of the vibration plate 16where the piezoelectric element 3 is fixed.

Next, the configuration of the piezoelectric element 3 is described withreference to FIGS. 1A and 1B.

As shown in FIG. 1A, the piezoelectric element 3 has the upper electrode40 as the common electrode and is formed by being laminated on thevibration plate 16.

In other words, as shown in FIG. 1B, the lower electrode 20 having alayer, which contains at least one of platinum (Pt), iridium (Ir) andtitanium (Ti), is laminated immediately above the vibration plate 16.The lower electrode 20 is an individual electrode and is formed forevery four piezoelectric elements in the embodiment. Of course, that thenumber of piezoelectric elements is four is an example and the inventionis not limited thereto.

In addition, the piezoelectric layer 30 including at least lead (Pb),zirconium (Zr) and titanium (Ti) is laminated immediately above thelower electrode 20. The piezoelectric layer 30 is configured by aperovskite type oxide and is configured by lead zirconate titanate whichincludes Pb in an A site element and Zr and Ti are included in a B siteelement. As described above, the perovskite type oxide may be aperovskite type oxide having a composition indicated in the generalformulae described below.

Pb(Zr,Ti)Ox  (1)

(Pb,MA)(Zr,Ti)Ox  (2)

Pb(Zr,Ti,MB)Ox  (3)

(Pb,MA)(Zr,Ti,MB)Ox  (4)

Here, MA is one or more metal elements excluding Pb and MB is one ormore types of metal elements excluding Zr, Ti and Pb. As for x, 3 is astandard, however, it may shift from 3 in a range in which theperovskite structure may be obtained. As for the ratio between the Asite element and the B site element, 1:1 is a standard, however, it maybe shifted from 1:1 in a range in which the perovskite structure istaken.

The MB element includes Nb (niobium), Ta (tantalum) or the like.

In addition, that the piezoelectric layer 30 is formed of lead zirconatetitanate is only an example and in addition thereto, it may be formed ofa piezoelectric material having a composition of (Bi,Ba)(Zr,Ti)Ox thatis a lead-based piezoelectric material or a non-lead-based piezoelectricmaterial.

The upper electrode 40 is laminated immediately above the piezoelectriclayer 30. The upper electrode 40 is the common electrode which is commonin all the piezoelectric elements 3 and is formed on each piezoelectriclayer 30 in succession. The metal constituting the upper electrode 40may use iridium (Ir), gold (Au), platinum (Pt), or the like. Of course,in addition thereto, it may contain metals different from the metalsdescribed above.

As shown in FIG. 1B, an end portion of the lower electrode 20 in thelongitudinal direction is extended further to the outside than an endportion of the pressure generation chamber 12 in the longitudinaldirection. In addition, an end portion of the upper electrode 40 in thelongitudinal direction, where the patterning is performed correspondingto each pressure generation chamber 12, is positioned before the endportion of a region where the lower electrode 20 is formed in thelongitudinal direction. In addition, the end portion of the upperelectrode 40 in the longitudinal direction is extended further to theoutside than the end portion of the pressure generation chamber 12 inthe longitudinal direction. In other words, the piezoelectric layer 30has a region which is positioned on the lower electrode 20 and is notcovered by the upper electrode 40, and a region which is positioned onthe lower electrode 20 and is covered by the upper electrode 40. Ofcourse, the positional relationship between the end portions of thelower electrode 20 and the upper electrode 40 in the longitudinaldirection is merely an example and for example, the end portion of theupper electrode 40 in the longitudinal direction may be formed beforethe end portion of the pressure generation chamber 12 in thelongitudinal direction.

In addition, a region, which is deformed by action of the electricfield, is defined as an active section 3 a and a region, which is notdeformed by the action of the electric field is defined as a non-activesection 3 b in the piezoelectric element 3. In the piezoelectric element3 illustrated in FIG. 1B, the active section 3 a is the region in whichthe lower electrode 20 is provided and the upper electrode 40 isprovided in the region in which the piezoelectric layer 30 is provided,and the non-active section 3 b is the region in which the lowerelectrode 20 is provided and which is not covered by the upper electrode40 in the region in which the piezoelectric layer 30 is provided. Inaddition, since the boundary of the active section 3 a and thenon-active section 3 b is also influenced by the position of thegenerated electric field, the boundary is not necessarily defined by theposition of the lower electrode 20 and the upper electrode 40 describedabove.

A protection film 80 is formed at the region which includes the boundaryof the active section 3 a where the upper electrode 40 is formed and thenon-active section 3 b in the piezoelectric layer 30 in order to coverthe region. In FIG. 1B, the protection film 80 is formed on thepiezoelectric layer 30 to cover the region which is not covered by theupper electrode 40 above the lower electrode 20.

Here, it is understood that cracking or the burnout caused by crackingmay occur remarkably near the boundary of the active section 3 a and thenon-active section 3 b in the piezoelectric layer 30. It is known thatas one causes thereof, the upper electrode 40 is formed by patterning orthe wiring is formed by patterning after the upper electrode film isformed on the piezoelectric layer 30 in the piezoelectric element 3having the upper electrode 40 as the common electrode, and chemicals orthe like are attached on the piezoelectric layer 30 when performing thepatterning and the composition of the piezoelectric layer 30 isunstable. In addition, as another cause, there is stress concentrationdue to unevenness in state of the occurrence of distortion in thepiezoelectric layer 30 near the boundary of the active section 3 a andthe non-active section 3 b in the piezoelectric layer 30. Thus, theprotection film 80 is formed to cover the boundary of the active section3 a and the non-active section 3 b and then the region has aconfiguration which decreases the occurrence of the cracking and theburnout.

In addition, it is preferable that the end portion of the upperelectrode 40 be formed before above the pressure generation chamber 12in the longitudinal direction of the protection film 80. In other words,it is preferable that the protection film 80 not be formed upwards theregion where the pressure generation chamber 12 is formed. Theprotection film 80 is formed away from the region in which the pressuregeneration chamber 12 is formed so that the piezoelectric element 3 isprevented from hindering the drive.

As the material of the protection film 80, an organic material such aspolyimide (aromatic polyimide) may be used. When the protection film 80is formed from polyimide, it is preferable that the thickness of thefilm be 1.7 μm or more. In addition, besides this, the protection film80 may be formed from an epoxy-based adhesive or silicon-based adhesive.In addition, when the protection film 80 is formed by the adhesive, itis preferable that the thickness of the film be 1.6 μm or more.

When the protection film 80 is the organic protection film, theprotection film 80 may be easily formed.

2. Manufacturing Method of Piezoelectric Element and Liquid EjectingHead

Manufacturing method of the piezoelectric element 3 and the recordinghead (the liquid ejecting head) 1 including the piezoelectric element 3described above is described with reference to FIGS. 2 to 4. Inaddition, here, the description is given as an example in a case wherethe polyimide (the organic protection film) is used as the protectionfilm 80.

As the manufacturing method of the recording head 1, first, the flowpath formation substrate 10 is formed of a silicon single-crystalsubstrate. An elastic film (the vibration plate 16) consisting ofsilicon dioxide (SiO₂) is for example, integrally formed by performingthermal oxidation of the silicon substrate 15 having a film thickness ofabout 625 μm that is relatively thick and has a high stiffness, in adiffusion path at about 1100° C. The thickness of the elastic film isnot limited as long as the film has elasticity, and for example, may beabout 0.5 to 2 μm.

Next, as shown in FIG. 3A, a lower electrode film is formed by asputtering method or the like in order to configure the lower electrode20 on the vibration plate 16. As the configuring metal of the lowerelectrode 20, one or more metals of Pt, Au, Ir, Ti and the like may beused. The thickness of the lower electrode is not specifically limitedand for example, may be about 50 to 500 nm. In addition, as a coherencelayer or a diffusion blocking layer, the lower electrode 20 may beformed after a layer such as TiAlN (titanium nitride aluminum) film, Irfilm, IrO (iridium oxide) film, ZrO₂ (zirconium oxide) film or the likeis formed on the vibration plate 16.

Next, a precursor solution including at least lead salt, zirconium saltand titanium salt is coated on the surface of the lower electrode 20.The metal molar concentration ratio in the precursor solution may bedetermined according to the composition of the perovskite type oxidewhich is formed. In the formulae (1) to (4) described above, as the moleratio of the A site element and the B site element, 1:1 is a standard,and it may be shifted from 1:1 in a range in which the perovskite oxideis formed.

The precursor solution coated as shown in FIG. 3A is crystallized andthen the piezoelectric layer 30 is formed. As an example, preferably,the precursor solution is heated to about 140° C. to 190° C. and dried,after that, for example, is heated to about 300° C. to 400° C. anddefatted, and then for example, is heated to about 550° C. to 850° C.and then crystallized.

In addition, in order to thicken the piezoelectric layer 30, acombination of a coating process, a drying process, a defatting processand a calcination process may be performed several times. In order toreduce the calcination process, the calcination process may be performedafter the combination of the coating process, the drying process and thedefatting process is performed several times. Further, these combinationof the processes may be performed several times. In the exampleillustrated in FIG. 3B, the lower electrode 20 and the piezoelectriclayer 30 are patterned on the region opposite each pressure generationchamber 12, after forming the piezoelectric layer 30 on the lowerelectrode film 20.

In addition, a heating device for performing the drying and thedefatting described above may use an infrared lamp annealing deviceheated by a hot plate and irradiation of an infrared lamp. In addition,the heating device for performing the calcination described above mayuse the infrared lamp annealing device or the like. It is preferablethat the temperature rising rate be relatively fast using RTA (RapidThermal Annealing) or the like.

As shown in FIG. 3B, the upper electrode 40 is formed on thepiezoelectric layer 30 formed described above using the sputteringmethod or the like. As the metal configuring the upper electrode, atleast one of metals of Ir, Au, Pt or the like may be used. The thicknessof the upper electrode is not specifically limited and, for example, maybe about 10 to 200 nm. In addition, in the example illustrated in FIG.3C, the upper electrode film is patterned on the region opposite eachpressure generation chamber 12 and then the piezoelectric element 3 isformed, after forming the upper electrode film.

Next, a lead electrode 45 is formed. For example, as shown in FIG. 3C,after forming the metal over the front surface of the flow pathformation substrate 10, the patterning is performed for eachpiezoelectric element 3 through the mask pattern configured of theresist or the like and then the lead electrode 45 is provided (FIG. 4A).The lead electrode 45 extending from the vicinity of end portion of theink supply path 14 side to the vibration plate 16 is connected to eachlower electrode 20 shown in FIG. 2.

The lower electrode 20, the upper electrode 40 or the lead electrode 45can be formed using a sputtering method such as a DC (direct current)magnetron sputtering method. The thickness of each layer may be adjustedby changing the application voltage or a sputtering process time of thesputtering device.

In addition, as shown in FIG. 4A, the protection film 80 is formed tocover the boundary of the active section and the non-active section ofthe piezoelectric layer 30. As the formation method of the protectionfilm 80, for example, first, the polyimide film is formed on thepiezoelectric layer 30 including the upper electrode 40. Next, forexample, the patterning is performed on the layer of the polyimide viathe mask pattern configured of the resist or the like and the dryetching is performed, thereby forming the protection film 80. Inaddition, when the photosensitive polyimide is used as the protectionfilm 80, the exposure and the development are performed and thenpatterning may be performed using the mask pattern, after filmformation.

As described above, the piezoelectric element 3 having the piezoelectriclayer 30 and the electrodes (20 and 40) is formed, and a piezoelectricactuator including the piezoelectric element 3 and the vibration plate16 is formed.

Next, as shown in FIG. 4B, the protection substrate 50 having apiezoelectric element holding section 52 or the like beforehand isjoined on the flow path formation substrate 10, for example, using anadhesive. As the protection substrate 50, for example, a siliconsingle-crystal substrate, glass, ceramic material or the like may beused. The thickness of the protection substrate 50 is not specificallylimited, and it may be for example, about 400 μm. A reservoir section51, which penetrates the protection substrate 50 in the thicknessdirection, configures a reservoir 9 that is a common ink chamber withthe communication path 13. The piezoelectric element holding section 52provided at the region opposite the piezoelectric element 3 hassufficient space to not obstruct the movement of the piezoelectricelement 3. The vicinity of the end portion of the lead electrode 45,which is drawn out from each piezoelectric element 3, is exposed to athrough hole 53 of the protection substrate 50.

Next, after polishing the silicon substrate 15 to a certain thickness,wet etching is performed using fluonitric acid and then the siliconsubstrate 15 is a predetermined thickness (for example, about 70 μm).Next, as shown in FIG. 4B, a mask film 17 is newly formed on the siliconsubstrate 15 and the patterning is performed in a predetermined shape.As the mask film 17, silicon nitride (SiN) or the like may be used.Next, anisotropic etching (wet etching) is performed on the siliconsubstrate 15 using alkaline solution such as KOH. Accordingly, aplurality of liquid paths including the pressure generation chamber 12partitioned by a plurality of partition walls 11 (see, FIG. 2) andnarrow ink supply path 14, and the communication path 13 that is thecommon liquid path connected to each ink supply path 14 are formed. Theliquid paths (12 and 14) are arranged in the width direction D1 which isa lateral direction of the pressure generation chamber 12.

In addition, the pressure generation chamber 12 may be formed before theformation of the piezoelectric element 3.

Next, as shown in FIG. 4C, the nozzle plate 70 is joined to a side ofthe silicon substrate 15 that is opposite the protection substrate 50.As the nozzle plate 70, glass, ceramic, a silicon single-crystalsubstrate, stainless steel or the like may be used. The nozzle plate 70is fixed to the opening side of the flow path formation substrate 10. Inorder to fix the adhesive, a thermal welding film or the like may beused. A nozzle opening 71, which communicates with the vicinity of theend portion opposite the ink supply path 14 of each pressure generationchamber 12, is penetrated into the nozzle plate 70. Accordingly, thepressure generation chamber 12 communicates with the nozzle opening 71discharging the liquid.

Next, the compliance substrate 60 having a sealing film 61 and a fixingplate 62 is joined on the protection substrate 50. As the sealing film61, for example, a material which is formed of polyphenylene sulfide(PPS) film having a thickness of about 6 μm and low stiffness andflexibility may be used. The sealing film 61 seals one side surface ofthe reservoir section 51. As the fixing plate 62, for example, a hardmaterial such as the metal of stainless steel (SUS) having a thicknessof about 30 μm may be used. A region opposite the reservoir 9 is anopening 63.

In addition, a driving circuit 65 for driving the piezoelectric elements3, which are arranged in parallel, is fixed on the protection substrate50. As the driving circuit 65, a circuit substrate, a semiconductorintegrated circuit (IC), or the like may be used. The driving circuit 65and the lead electrode 45 are electrically connected via a connectionwiring 66. As the connection wiring 66, a conductive wire or the likesuch as a bonding wire may be used.

As described above, the recording head 1 is manufactured.

The recording head 1 loads the ink from an ink induction port connectedto the outside ink supply unit (not shown) and fills the inside thereofwith the ink from the reservoir 9 to the nozzle opening 71. When thevoltage is applied to between the lower electrode 20 and the upperelectrode 40 for each pressure generation chamber 12 according to therecording signal from the driving circuit 65, ink droplets aredischarged from the nozzle opening 71 due to the deformation of thepiezoelectric layer 30, the lower electrode 20 and the vibration plate16.

3. Liquid Ejecting Apparatus

FIG. 5 illustrates an external appearance of a recording apparatus(liquid ejecting apparatus) 200 having the recording head 1 describedabove. When the recording head 1 is assembled into recording head units211 and 212, the recording apparatus 200 may be manufactured. Therecording apparatus 200 shown in FIG. 5 is configured in such a mannerthat the recording head 1 is provided in each of recording head units211 and 212, and ink cartridges 221 and 222, which are outside inksupply units, are detachably provided. A carriage 203 having therecording head units 211 and 212 is provided so as to be movablereciprocally along a carriage shaft 205 attached to an apparatus mainbody 204. When driving force of a driving motor 206 is transmitted tothe carriage 203 via a plurality of gears (not shown) and a timing belt207, the carriage 203 moves along the carriage shaft 205. A recordingsheet 290, which is fed using a feeding roller (not shown) or the like,is transported on a platen 208 and the print is performed on therecording sheet using the ink which is supplied from the ink cartridges221 and 222 and discharged from the recording head 1.

4. Embodiment

Hereinafter, the embodiment is illustrated and the invention is notlimited to the example described below.

Here, the ink jet type recording heads of the embodiments 1 to 3described below were manufactured and a DC electricity test wasperformed on the piezoelectric element.

Embodiment 1

The ink jet type recording head was the embodiment 1 which has theprotection film configured from the polyimide having the film thicknessof 0.7 μm to cover the end portion of the active section (vicinity ofthe boundary of the active section and the non-active section) in thepiezoelectric element. The Young's modulus E of the polyimide is 3.0GPa.

Embodiment 2

The ink jet type recording head similar to the embodiment 1 was anembodiment 2 besides the protection film configured from the polyimidehaving the film thickness of 2.6 μm.

Embodiment 3

The ink jet type recording head similar to the embodiment 1 was anembodiment 3 besides the protection film configured from the adhesivehaving the film thickness of 3.0 μm. In addition, the Young's modulus Eof the adhesive is 3.0 GPa.

Table 1 illustrates each condition (the film thickness t, the Young'smodulus E, product of the Young's modulus and the film thickness: E×t)of the embodiments 1 to 4 and the states of the burnout at the endportions of the active section, when performing evaluation ofwithstanding voltage. A case of “◯” indicates that the burnout did notoccur and a case of “Δ” indicates that the burnout decreased compared toa case where the protection film is not formed.

TABLE 1 Film Young's Material Thickness (t) Modulus (E) E × t BurnoutEmbodiment 1 Polyimide 0.7 μm 3 GPa 2100 Δ Embodiment 2 Polyimide 2.6 μm3 GPa 7800 ∘ Embodiment 3 Adhesive 3.0 μm 3 GPa 9000 ∘

As shown in Table 1, in the embodiments 2 and 3 where the product of theYoung's modulus E and the film thickness t is 7800 (Pa·m) or more, theburnout was observed at the end portion of the active section 3 a. Inaddition, in the embodiment 1 where the product of the Young's modulus Eand the film thickness t is 2100 (Pa·m), a decrease in the burnout wasobserved at the end portion of the active section 3 a.

As described above, it was understood that the protection film 80 isformed to cover the boundary of the active section 3 a and thenon-active section 3 b and then the burnout is suppressed. In addition,it was understood that when the product of the Young's modulus E and thefilm thickness t is 2000 (Pa·m) or more, the burnout may be decreasedand more preferably, when the product of the Young's modulus E and thefilm thickness t is 7800 (Pa·m) or more, the burnout did not occur.

5. Second Embodiment

Hereinafter, as the second embodiment, a case where the protection film80 is an inorganic protection film is described. FIGS. 6A to 6C arecross-sectional views for illustrating a manufacturing process of therecording head 1. FIGS. 7A to 7C are cross-sectional views forillustrating a manufacturing process of the recording head 1.

The protection film 80 according to the second embodiment is the same asthat of the first embodiment in the configuration where the protectionfilm 80 covers the boundary of the active section 3 a and the non-activesection 3 b in the piezoelectric layer 30. Meanwhile, the secondembodiment differs from the first embodiment in that sequence of aprocess in which the protection film 80 is formed is immediately after aprocess in which the upper electrode 40 is formed. It is caused by theprotection film 80 that is formed using the inorganic material in thesecond embodiment, while the protection film 80 is formed using theorganic material in the first embodiment.

As an example, the protection film 80 according to the second embodimentis formed from, for example, aluminum oxide (Al₂O₃) as the inorganicprotection film. In addition, in a case where the protection film 80 isformed from Al₂O₃, it is preferable that the film thickness be 25 nm ormore.

The manufacturing method of the piezoelectric element 3 and therecording head (liquid ejecting head) 1 including the piezoelectricelement 3 described above is described with reference to FIGS. 6A to 7C.Further, a case where Al₂O₃ (inorganic protection film) is used as theprotection film 80 is described as an example. In addition, eachcondition when configuring the recording head 1 is the same as that ofthe first embodiment.

First, similar to the first embodiment, the flow path formationsubstrate 10 is formed from the silicon single-crystal substrate or thelike. The elastic film (the vibration plate 16) configured of silicondioxide (SiO₂) is integrally formed by performing thermal oxidation ofthe silicon substrate 15, in the diffusion path of about 1100° C.

Next, as shown in FIG. 6A, the lower electrode 20 is formed by thesputtering method or the like on the vibration plate 16. As shown inFIG. 6B, the piezoelectric layer 30 is formed by crystallizing thecoated precursor solution. As shown in FIG. 6B, the upper electrode 40is formed by the sputtering method or the like on the piezoelectriclayer 30 formed as described above.

In addition, the protection film 80 is formed to cover the boundary ofthe active section 3 a and the non-active section 3 b of thepiezoelectric layer 30. As the formation method of the protection film80, as shown in FIG. 6C, first, the film of Al₂O₃ is coated on thepiezoelectric layer 30 including the upper electrode 40. Next, forexample, the patterning is performed on the layer of aluminum oxide viathe mask pattern configured of the resist or the like and the dryetching is performed and then the protection film 80 is formed.

Next, as shown in FIG. 7A, the lead electrode 45 is formed on theprotection film 80. For example, patterning is performed for eachpiezoelectric element 3 through the mask pattern configured of theresist and the like and then the lead electrode 45 is provided, afterforming the metal layer over the front surface of the flow pathformation substrate 10. In other words, in the second embodiment,patterning is performed to form the lead electrode 45, after theprotection film 80 is formed. Thus, the piezoelectric layer 30 may beprotected by the protection film 80 from the chemicals used whenpatterning the lead electrode 45.

In addition, as shown in FIG. 7B, the protection substrate 50 having apiezoelectric element holding section or the like beforehand is joinedon the flow path formation substrate 10, for example, using theadhesive. Next, the mask film 17 is newly formed on the siliconsubstrate 15 and the patterning is performed in a predetermined shape.In addition, as shown in FIG. 7C, the nozzle plate 70 is joined to theside of the silicon substrate 15 opposite the protection substrate 50.Next, the compliance substrate 60 having the sealing film 61 and thefixing plate 62 is joined on the protection substrate 50 and is dividedinto a predetermined chip size. As described above, the recording head 1is formed.

6. Embodiment

Hereinafter, embodiments according to the second embodiment areillustrated and the invention is not limited to the examples describedbelow.

Here, the ink jet type recording head of the embodiment 4 describedbelow was manufactured and the DC electricity test was performed on thepiezoelectric element.

Embodiment 4

The ink jet type recording head was the embodiment 4 which has theprotection film configured from Al₂O₃ having the film thickness of 90 nmto cover the end of the active section (the vicinity of the boundary ofthe active section and the non-active section) of the piezoelectriclayer configuring the piezoelectric element. The Young's modulus E ofthe Al₂O₃ is 200 GPa.

Embodiment 5

The ink jet type recording head similar to the embodiment 4 was anembodiment 5 besides the protection film configured from Al₂O₃ havingthe film thickness of 45 nm.

Table 2 illustrates each condition (the film thickness t, the Young'smodulus E, the product of the Young's modulus and the film thickness:E×t) of the embodiments 4 and 5, and illustrates the presence or absenceof the burnout at the end portions of the active section, whenperforming evaluation of withstanding voltage.

TABLE 2 Film Young's Material Thickness (t) Modulus (E) E × t BurnoutEmbodiment 4 Al₂O₃ 90 nm 200 GPa 9000 ∘ Embodiment 5 Al₂O₃ 45 nm 200 GPa4500 ∘

As shown in Table 2, also in the second embodiment, it was understoodthat the burnout of the piezoelectric layer is decreased. In otherwords, the burnout was observed at the end portion of the active sectionin the protection film where the product of the Young's modulus E andthe film thickness t is 4500 (Pa·m) or more.

According to the first embodiment and the second embodiment, the burnoutmay be suppressed at the end portion of the active section, when theproduct of the Young's modulus E and the film thickness t is 5000 (Pa·m)or more.

Thus, it was understood that the protection film is formed at theboundary of the active section and the non-active section using theinorganic material and then the burnout is suppressed.

7. Application and Others

As for the invention, various modification examples may be considered.

In the embodiments described above, individual piezoelectric body isprovided for each pressure generation chamber, however, a commonpiezoelectric body may be provided at a plurality of pressure generationchambers and individual electrode may be provided for each pressuregeneration chamber.

In the embodiments described above, a portion of the reservoir is formedat the flow path formation substrate, however, the reservoir may beformed at a member different from the flow path formation substrate.

In the embodiments described above, the upper side of the piezoelectricelement is covered by the piezoelectric element holding section,however, the upper side of the piezoelectric element may be opened tothe atmosphere.

In the embodiments described above, the pressure generation chamber isprovided across the vibration plate opposite the piezoelectric element,however, the pressure generation chamber may be provided at thepiezoelectric element side. For example, when a space, which issurrounded between the fixed plates and between the piezoelectricelements, is formed, the space may be the pressure generation chamber.

The liquid discharged from the liquid ejecting head may be a materialwhich is capable of being discharged from the liquid ejecting head andincludes liquids such as a solution in which dye or the like isdissolved in solvent, sol in which solid particles such as pigment ormetal particles are dispersed to a dispersion medium. The liquidincludes inks, liquid crystals, or the like. The liquid ejecting headmay be provided in a manufacturing apparatus of a color filter such as aliquid crystal display, or the like, a manufacturing apparatus of theelectrode such as an organic EL display, or the like, a manufacturingapparatus of a biochip, or the like, besides an image recordingapparatus such as a printer.

As described above, according to the invention, technique, whichimproves the performance of the piezoelectric element having at leastpiezoelectric layer, the liquid ejecting head and the liquid ejectingapparatus, may be supplied by various embodiments.

In addition, a configuration which replaces each of the configurationsdisclosed in the embodiments and modification examples described aboveto each other or changes combination thereof, a configuration whichreplaces each of configurations disclosed in the related art, theembodiments and modification examples described above to each other orchanges combination thereof, or the like may be carried into effect. Theinvention also includes the configurations.

What is claimed is:
 1. A piezoelectric device comprising: a substratehaving a first major surface and a second major surface; a chamberformed in the substrate, the chamber including a sidewall having a firstend at the first major surface and a second end at the second majorsurface; a first electrode formed on the first major surface ofsubstrate, and overlapping the first end; a piezoelectric layer formedon the first electrode; a second electrode formed on the piezoelectriclayer; and a protection layer formed on the piezoelectric layer and thesecond electrode, wherein the protection layer is laterally offset fromthe first end in a plan view.